Crosslinked polyrotaxanes are produced by crosslinking polyrotaxanes in which capping groups are individually introduced at each end of a pseudopolyrotaxane. For example, in cases where a pseudopolyrotaxane comprises a compound having a polyethylene glycol (hereinafter, also referred to as “PEG”) chain (hereinafter, also referred to as a “PEG compound”) and a cyclodextrin that includes the PEG compound, the resulting crosslinked polyrotaxane has a structure in which a PEG chain of the PEG compound threads through the cyclodextrin in a skewered manner and the cyclodextrin is movable along the PEG chain by a pulley effect. The pulley effect allows the crosslinked polyrotaxane to uniformly distribute tensile force applied thereto. The crosslinked polyrotaxane is therefore not likely to have cracks or flaws, i.e., has excellent characteristics that conventional crosslinked polymers do not have.
Patent Literature 1 discloses a method for producing a polyrotaxane including: dissolving separately carboxylated polyethylene glycol having a PEG chain in which both end groups are carboxylated and α-cyclodextrin in warm water at 70° C., mixing the solutions together and cooling the mixture to prepare an aqueous dispersion of pseudopolyrotaxane, freeze-drying the aqueous dispersion to prepare a pseudopolyrotaxane, and reacting the resulting pseudopolyrotaxane with adamantanamine in dimethylformamide in the presence of a BOP reagent (benzotriazole-1-yl-oxy-tris(dimethylamino)phosphonium hexafluorophosphate) as a condensing agent and diisopropylethylamine as a catalyst.